Dr. Mohy Morris, the P.I., is an assistant professor who completed his Pediatric Pulmonary Fellowship in 1994. In this proposal he outlines a program to study healthy infants and patients with wheezing using new infant lung function tests (ILFT). The general hypothesis is that newer ILFT will be more reliable than previous tests in defining infant lung growth and in differentiating healthy infants from wheezers. Determining the nature of infant wheezing, is also a major goal of this investigation. Respiratory diseases are the most prevalent of all chronic childhood illnesses. ILFT are important in the diagnosis and management of respiratory diseases. They are also essential to our understanding of their acute or chronic effects and to our ability to prevent or minimize these effects. The P.I. will use his novel noninvasive technique for measuring the residual volume (RV) by the nitrogen washout technique. The rapid thoraco-abdominal compression (RTC) technique has been widely used within the tidal range to induce a forced expiration in infants. Flow limitation may not be achieved. The P.I. proposes the performance of RTC from a raised lung volume to an airway opening pressure of 30 cm H20 to generate a forced expiration with sufficient transpulmonary pressure to attain flow limitation. Flows are then independent of effort to reflect lung mechanics. Tested hypotheses will be that: (1) RV is a more reliable measurement of volume than the functional residual capacity, the only lung volume routinely assessed in infants, and is an early indicator of air trapping; (2) variables of forced expiration are reproducible and dependent on the age, length, weight of the infant but are lower in blacks than in whites; (3) flows are low in airways disease; (4) depending on the underlying pathology, flows may or may not increase after giving a bronchodilator drug. Since ILFT are not yet standardized, the finding of a suitable variable(s) will enhance a better design of prevention or therapeutic strategies in children. The P.I. will take advantage of the significant protected research time, strong mentoring and outstanding resources at the University of Arkansas for Medical Sciences and Arkansas Children?s Hospital to become an independent investigator in Pediatric Pulmonology patient-oriented research.